A cataract is a disease in which the crystalline lens of the eye becomes opaque, leading to a decrease in vision. In this case, when the edge of the crystalline lens becomes opaque, the cataract does not significantly affect vision, but various symptoms such as decreased visual acuity, diplopia, dazzling, and the like appear when a nuclear zone of the crystalline lens becomes opaque. The treatment for a cataract generally consists of removing an opaque crystalline lens and replacing it with an artificial intraocular lens through surgery. Such cataract surgery is one of the most widely performed surgical procedures.
Conventional cataract surgery is performed using a method which includes incising a cornea with a knife, circularly incising an anterior capsule of a crystalline lens through the incised region of the cornea, finely pulverizing the nucleus of a crystalline lens using ultrasonic waves, extracting the nucleus of the crystalline lens by suction, and inserting another intraocular lens into the region from which the nucleus of the crystalline lens was removed.
Such a cataract surgery method is similarly disclosed in Korean Unexamined Patent Application Publication No. 1990-0015698.
In such cataract surgery, the anterior capsule of the crystalline lens is preferably incised in the form of a circle or as close as possible because of the following reasons.
First, when the anterior capsule of the crystalline lens is removed in one piece, a situation in which surgery in a future operative stage is hindered because the presence of the anterior capsule of the crystalline lens may be prevented.
Second, lens luxation may be prevented because a force applied to the anterior capsule of the crystalline lens during the surgery may be uniformly spread to disperse a force applied to a ligament of the crystalline lens.
Third, the eye may be in a stable close system when the anterior capsule of the crystalline lens is incised in a circle, thereby preventing damage to a posterior capsule.
Fourth, when intracapsular manipulations (nuclear segregation, nuclear fragmentation, intraocular lens manipulating, etc.) are performed during the surgery, surgical complications may be reduced due to high physical stability.
Fifth, the contraction and opacification of the capsule after the surgery may be prevented, thereby preventing blurred vision which may recur after the surgery.
Also, in addition to the incision shape upon incision of the anterior capsule, an incision size is an important factor determining the success or failure of the surgery. Generally, the size of an incised section is preferably slightly smaller than that of an optical zone of an intraocular lens. When the size of the incised section is larger than that of the optical zone of the intraocular lens, the lens luxation, iris incarceration or dislocation, etc. may occur, leading to blurred vision, and a reoperation should be performed when the blurred vision is severe.
On the other hand, when the size of the incised section is too small, the contraction of the sac may occur to conceal the visual axis, thereby causing blurred vision, the opacification of the anterior capsule of the crystalline lens and posterior capsule may be caused, thereby requiring an additional surgical operation, and the dislocation of the intraocular lens may be caused, thereby deteriorating the quality of vision after the surgery. Korean Unexamined Patent Application Publication No. 2011-0084887 discloses a device for capsulorhexis.
In recent years, the importance of incision of the anterior capsule of the crystalline lens with a perfect circle and proper size has increased with an increase in the use of multifocal intraocular lenses for presbyopic correction, and intraocular lenses for correction of astigmatism. In the case of these intraocular lenses, postoperative complications, such as lens dislocation, posterior capsular opacity, and the like have a larger effect on vision acuity than the unifocal intraocular lenses, and additional manipulations themselves performed to address occurring complications may cause degradation in the performance of the intraocular lenses.
Meanwhile, another factor determining the success or failure of the surgery is an incision location of the anterior capsule. When the incision location of the anterior capsule of the crystalline lens deviates from the center of the crystalline lens, the dislocation and slope of the crystalline lens, and the like may occur, and postoperative posterior capsular opacity may easily occur, resulting in degraded surgical efficiency.
Generally, experienced surgeons incise an anterior capsule of the crystalline lens based on the size of a patient's cornea, and the size of a dilated pupil. However, since individual patients have different cornea sizes and the dilated pupils are not uniform in size, the final size and location may not be fixed.
Since the incision shape and location of the anterior capsule of the crystalline lens fully depend on the surgeons' experience and techniques, it is very difficult to incise the anterior capsule of the crystalline lens in a perfect circle and a proper location. Also, when the incision size and shape of the anterior capsule of the crystalline lens is not perfect, an additional surgical procedure should be performed to adjust the size of a capsule of the crystalline lens after insertion of the intraocular lens, resulting in wasted time and effort.
Since the incision of the anterior capsule of the crystalline lens itself is a very elaborate surgical procedure as described above, a method capable of guiding an exact size and location during the incision of the anterior capsule of the crystalline lens is required.